The grove, after the cave, was the most popular uterine symbol in the ancient religions, even among the early biblical Semites, to whom Asherah (or Aserah) was the Mother-goddess of the grove. Usually a large tree, pillar, or obelisk with the grove represented the male god inside the goddess as both child and lover.
Brittany in the 11th century still had a Druidic holy wood called Nemet. This was probably the same name as the fairy wood Broceliande, the grove of Merlin’s Nemesis, the lady Nimue, who also bore the name of the fatal goddess of the grove.
Groves began to be considered dangerous with the emergence of the patriarchal priesthoods, especially in early biblical times when the Bible mentions attacks on the asherim, or the Groves of Asherah, which were consistently worshipped by both people and kings, despite the prophets’ repeated condemnation.
Those who destroyed these sacred groves feared the Mother’s curse, as demonstrated in numerous moralizing myths. Erysichthon dared to cut down one of Demeter’s sacred groves, though the high priestess forbade him with the voice of the Goddess herself. Then angry Demeter cursed him with perpetual hunger that could never be appeased. He became a wretched beggar, frantically stuffing his mouth with filth.
The Druids held ceremonies, prayers, libations and human sacrifices, in sacred groves, which at the time were revered as temples are today. These sacred enclosures also were places of assemblies were decisions were made and administration of justice in civil and criminal disputes was dispensed.
When groves were not available assemblies met by sources of water, such as lakes and rivers, because the Celts worshipped water gods and believed water to be sacred.
However, trees, especially the oak, were the most sacred; the term Druid means “knowing the oak tree.” The oak grove at Derry was one of the most popular shrines in Irish paganism; another was Diana’s ancient grove at Lake Nemi, where sacred kings fought any challenger who broke a branch from the sacred tree.
There is evidence that shows that to break the branch was liken to castrating the god or incumbent sacred king who embodied the god. A.G.H.
Walker, Barbara G, The Woman’s Encyclopedia of Myths and Secrets, New York, HarperCollins, 1983, pp. 356-357
Guiley, Rosemary Ellen, The Encyclopedia of Witches and Witchcraft, New York: Facts On File, 1989, p. 108